Engine lubrication systems provide many functions such as wear protection, corrosion protection, and engine cooling. One drawback is that engine power is diverted to operating a high pressure oil pump to distribute oil through passages in the engine, which weighs against engine efficiency. Overhead cam (OHC) engines present a challenge to adequately and reliably lubricate the valve train without creating an undue demand on the engine lubrication system.
In an internal chain-driven camshaft OHC engine, as the chain is driven around the cam sprocket, the centrifugal force creates a steady spray of oil from the chain and cam sprocket onto the cam cover. The oil drains into the engine oil reservoir without providing lubrication to valve train components. This source of unpressurized oil presents an opportunity for providing lubrication to valve train components.